I would recommend just 2 science-based books that will give you plenty to work with:

Influence: Science and Practice by Robert Cialdini (http://goo.gl/mTsLvl)

Brainfluence: 100 Ways to Persuade and Convince Consumers with Neuromarketing by Roger Dooley (http://goo.gl/dXa9cA)

They're fascinating and grounded in experimental data. I would recommend buying the kindle editions, underlining important points as you read them, and then copying all your underlined sections into a outline that you construct when you're done with each book. Then read back through the outline, consolidate it, and organize it.

By doing those steps you can absorb and understand the information to an extent that you can use it naturally, but don't be an ass and use it to give people something they don't want, or get them to do something they don't want. Use the knowledge to aid in getting your quality product to people that will actually be happy with it and thankful for it.